The present invention relates generally to a method of detecting the presence of an insult in an absorbent article while it is being worn by a wearer and a monitoring system for performing the method.
Absorbent articles associated with wetness indicators have been proposed to signal to a caregiver when the absorbent article has been insulted. One way of monitoring a toilet-training child is by using a system that detects a change in an electrical property of the undergarment when the electrical property is a function of the wetness of the undergarment. For example, the electrical property may be resistance, conductance, impedance, capacitance or any other parameter which varies as the wetness of the undergarment varies. For example, a pair of spaced apart parallel conductors may be situated within the absorbent material of the undergarment. These conductors are in electrical contact with the absorbent material of the undergarment and are connected to a sensing circuit for monitoring the electrical property, the circuit includes a power source, such as a battery. For example, the circuit may comprise a voltage divider for detecting resistance between the conductors. The output of the circuit is an analog output voltage that corresponds to a resistance value. When the undergarment is dry, the resistance between the conductors is extremely high and relatively infinite, appearing as an open circuit. When the undergarment is wet, more particularly when the absorbent material of the undergarment between the conductors becomes wet, the resistance of the undergarment at that area drops to a relatively lower value because urine acts as a conductor.
Accordingly, in a conventional system a sensor monitors the resistance between the conductors and compares resistance values to a predetermined and fixed threshold resistance value. If a resistance value is less than the threshold resistance value, then the sensing circuit (herein sensor) sends a signal to an alarm device, which informs the caregiver and/or the wearer that the wearer has urinated. For example, the alarm device may be a device for producing an auditory signal, such as a song, a visual signal, such as a light, or a tactile signal, such as a change in temperature.
For potty training and enuretic use of absorbent articles, it is typically useful for the caregiver and/or user to know immediately when an absorbent article has been insulted to allow for corrective action and the training process. For other uses of absorbent articles, the caregiver can benefit from knowing how many times the absorbent article has been insulted without necessarily being required to change and discard the absorbent article. This can be the case for newborns and infants. Even if the absorbent article is insulted with urine, caregivers often will not change the absorbent article until it contains a bowel movement or the absorbent article feels saturated with urine. Especially with newborns, the urine insults are typically very frequent and in small amounts. Regardless, after some time the caregiver will need to change the absorbent article for skin health reasons.